It was a time of peace and prosperity for Equestrian society. Princess Twilight Sparkle had ruled Equestria for five millennia and society had been revolutionized as a result of her teachings in friendship and her own scientific know-how. Really, the last time there had been any conflict was in the first century of Twilight's rule when a mad stallion named Nihil ordered a group of like-minded ponies called the Realm Ravagers to lay waste to the land in his own twisted sense of order. The only reason he was stopped was because he wanted revenge on Discord and, after finding out about his redemption, as well as seeing him mourning for Fluttershy since she passed away from old age, he called off his forces and signed a peace treaty with Twilight.
Living in Canterlot were two foals, a grey unicorn and a brown Earth pony, who were the best of friends. They bonded over their fascination with time and their desire to leave Equestria to explore the stars. Soon enough, the unicorn got old enough to attend the School for Gifted Unicorns, believing himself to be incredibly gifted and feeling that this is the only way he and his friend could truly find out the secrets to time-travel. While the entrance exam was the same as always, which was to hatch a baby dragon egg, the unicorn felt that was too easy and decided to practice a spell by using the Earth pony as a test subject. The unicorn was going to try and send his Earth pony friend into the future. He focused so hard, he thought he was going to burst a blood vessel. Then, his friend started swirling with arcane energy and suddenly disappeared in a magical explosion.
The Earth pony was sent hurtling through the time stream, mesmerised by all the colours and the images of past, present and future. That soon ended when he landed on his back in a barren wasteland. But it was not barren at all, for there were ponies battling one another. There was blood everywhere and one pony wearing a skull-like mask grabbed another pony by the head and smashed his head open in front of the terrified foal. And if that wasn't bad enough, he also bore witness to all sorts of monsters and abominations prowling across the ruined land with spindly legs and slithering tentacles. Along with the ponies wearing skull masks, there were hordes of travesties, Lava Demons, the Pony of Shadows, Clockworkers, and some sort of primordial chaos that would make Discord himself scared. If anypony has ever wondered what the pits of Tartarus looked like, this was probably as close as they were going to get. The Earth pony tried to run but everywhere he turned, there was something trying to kill him or somepony dying in his way. When he thought all hope was lost, he noticed a portal with a familiar grey hoof sticking out.
"Whooves!" a voice called out. He would have recognized that voice anywhere. It was the voice of his best friend.
Whooves immediately began to run as close to the portal as possible, trying desperately to avoid all the sharp objects and pony corpses along the way. He dashed through the portal and, when he got back to his time, he quickly and tightly embraced his unicorn friend and wept. From then on, Whooves decided that there was no way anypony had to go through what he had gone through and experience what he had witnessed. Time eventually past and the young colts eventually became stallions. In spite of what he had witnessed, Whooves actually managed to put the past behind him and grew up well-adjusted. And not only that, but he had his best friend helping him out with his studies regarding the science behind magic, maybe even finding a way for other races such as pegasi and Earth ponies to use magic the same way unicorns and alicorns could. But of course, such research could take centuries, even millennia, until they got results from it, so they have been experimenting with ways to slow down their ageing.
While Whooves had more success thanks in part to using techniques practised in cryogenic preservation to slow down his ageing and metabolism, his friend used magic and genetic splicing, which had the side effect of turning his eyes into that of a serpent. Oh well, at least it increased his ability to hypnotize people and he could even regenerate lost limbs. Though it would take further genetic splicing to be able to do that one. Time eventually passed and Whooves and his friend finally figured out how to make it possible for non-unicorn ponies to use magic, even if it's only the ability to manipulate time. And not only that, but they also found out a way to scan for ponies with a particular affinity for time-travel magic. After all, if it was possible for a pegasus to break the sound barrier and perform a Sonic Rainboom, then it is possible for some pegasi to fly so fast, they could even fly through time. And the same concept could easily apply to Earth ponies but with running instead of flying. But of course, such things are mostly basic and are limited to travelling into the future so they continued studying and experimenting for ways for Earth ponies and pegasi to use even more complex time-travel magic.
And that's when Whooves discovered, thanks to decades of self-experimentation, that he could now manipulate his own metabolism and even his own perception of time. He tried this theory out by throwing three balls in the air in an attempt to juggle them. By imagining them going slower than they actually are, he can actually catch one of them with one hoof and throw it into his other hoof with the ball floating in slow-motion. Of course, such process also made him very hungry. Now that he could slow down time, he wanted to find out he can speed it up. So he spent one day on a caffeine binge and running around his house until what was supposed to last twenty-four hours instead passed by in ten seconds (according to the count in his head anyway). But of course, why stop with going forward when you can go backwards too. While going back in time proved more difficult, he managed to do not by running, but by standing still and remembering the ten-second day and playing it in slow motion in his head until he pauses on a specific moment and goes from there. Excited by this discovery, he just had to tell his friend the good news. And so he came barging in while his friend was giving a lecture about time spells.
"Kronos!" Doctor said excitedly, speeding in like a bullet-train with electrical sparks zapping out of him. "IhaveexcellentnewsIhavefiguredoutawayfornonunicornstousemoreadvancedtimemagicthatinvolveschangingtheirperceptionoftimeandmanipulatingtheirmetabolis-"
Before he could finish his extraordinarily fast sentence, he suddenly disappeared out of thin air in a big zap. Kronos ran to make sure his friend was okay and found him collapsed onto the front porch of his house. When Whooves opened his eyes, he noticed Kronos was looking over him with a smile. In spite of the snake eyes, it was a warm smile, one you'd actually expect from a friend. Soon enough, they made their way to Twilight's castle to present their findings to her. Since Twilight herself had her fair share of time-travel escapades, she figured the best way to make sure nopony messed up the timeline was to have a group of ponies in charge of keeping an eye on time. But of course, such peace was never meant to last since the Realm Ravagers have returned and waged war on the Time-Turners. Both Kronos and Whooves did their bit in the war, with Whooves acting as a medic and Kronos being a general. But Whooves recognized where he had seen these horrors of war before, especially when he had a glimpse of a foal version of himself while healing one of the soldiers. After this revelation, he had a full-on panic attack and ran for his life. He bolted open the doors of Kronos' office, which was a bronze colour with a big portrait of Kronos on the right wall and a massive cuckoo clock on the left wall, and looked through Kronos' drawers for any time-spells. Unfortunately for him, that's when Kronos walked in with a golden seal in hoof.
"Doctor, might I ask what you're doing looking through my drawers?"
"Nothing. Just looking for a time-spell that might be beneficial to the war."
Whooves then looked at the seal Kronos was holding. It was golden and it was wearing a war helmet.
"Quite an unusual creature, Kronos," Whooves said in order to distract Kronos from the fact that he was trying to steal a time-spell written by Star-Swirl the Bearded, "What exactly is it, might I ask?"
"Oh, this? Oh, it's not much, just the Seal of War."
"Oh come along now! That is such a tasteless name to give the poor thing, even if it does look sort of adorable with that helmet."
"I wasn't the one who named it. It's called that because it's in charge of starting wars. Not only that, but it also feeds of the bloodshed of those wars."
Whooves' blood ran cold at that statement.
"W...What do you mean?"
"Since we're friends, I'm going to tell you a little secret."
Kronos walked closer to Whooves and whispered his plan in Whooves' ear. What Kronos said absolutely horrified Whooves. How can his best friend that he's known since they were foals be so willing to sacrifice so many lives just for the sake of power? And the worst thing was that the war Kronos was responsible for was the same war Whooves bore witness to when he was just a foal.
"You're a monster!" Whooves said, with disgust and horror in equal measure.
"I see no problem with that. After all, most monsters tend to be immortal. Isn't that what we wanted?"
"No! Our goal was to explore space and time! You're trying to destroy it!"
"True, but at least I'll make something better in its place."
And with that, Whooves pushed Kronos out of the way and ran as fast as he can to Twilight's castle to tell her of Kronos' treachery, in exchange for hiding away in the past so nopony could disturb his research and so Kronos didn't come looking for him. After all, if he could put his traumatic experience behind him when he was a foal, he could easily put this time behind him as well.